“So many senators coming together for an all-night session shows our commitment to wake up Congress to the dangers of climate change,” Sen. Barbara Boxer (D-Calif.), one of the founders of the task force, said in a statement.

Twenty-six Democrats and two independents are to participate.

“Climate change is real, it is caused by humans, and it is solvable,” said Sen. Brian Schatz (D-Hawaii). “Congress must act.” He and Sen. Sheldon Whitehouse (D-R.I.), the two organizers of the event, plan to give their colleagues a nap break from 1 a.m. to 6 a.m. when they dominate the floor.

A spokeswoman for Schatz, Meaghan Smith, said the task force does not plan to use the event to announce any new bills or concrete measures. “We’ll see” about introducing legislation this session, she said. “This isn’t a litmus test or anything.… This is really meant to galvanize momentum.”

Several top Democratic senators from coal-mining and oil-producing states who are facing competitive midterm races are conspicuously absent from the roster, including Sens. Kay Hagan of North Carolina, Mark Begich of Alaska and Mark Pryor of Arkansas.

Also absent will be Sen. Mary L. Landrieu (D-La.), who was appointed head of the Senate Committee on Energy and Natural Resources this year amid complaints from environmentalists within the Democratic Party.

The all-nighter will begin after the last votes are cast around 6 p.m. and will open with remarks from four Senate Democratic leaders: Harry Reid (D-Nev.), Richard J. Durbin (D-Ill.), Charles E. Schumer (D-N.Y.) and Patty Murray (D-Wash.). The senators will take turns speaking until 9 or 10 a.m. Tuesday.

There has been little talk of legislation to tackle climate change in Congress since 2010, when a bill to reduce carbon emissions died in the Senate.

But as they rev up for the midterm elections, Democrats are heeding the call of California billionaire Tom Steyer, who has pledged $100 million to back candidates with a program to curb climate change.

The campaign is intended to counter the Koch brothers, billionaire industrialists Charles and David Koch, who are behind some of influential political committees that have opposed legislation to reduce greenhouse gas emissions.

California is feeling the effects of climate change far and wide as heat-trapping greenhouse gases reduce spring runoff from the Sierra Nevada, make the waters of Monterey Bay more acidic and shorten winter chill periods required to grow fruit and nuts in the Central Valley, a new report says.